HIGHLY RESOLVED LARGE-EDDY SIMULATIONS OF A TRANSONIC COMPRESSOR STAGE MIDSPAN SECTION PART I: EFFECT OF INFLOW DISTURBANCES

Flows in modern compressors are highly complex. They are subject to adverse pressure gradients, high levels of unsteadiness and often operate at transonic conditions. Such conditions often render low order methods such as URANS unreliable. This is due to the inherently unsteady nature of shock-boundary layer interaction as well as the interaction between deterministic and stochastic unsteadiness. These issues are further exacerbated by the current design trends towards more compact machines with higher work coefficients. It is therefore desirable to study the flow within a transonic compressor stage using highly-fidelity scale resolving simulation. To enable fully wall resolved stage calculations at a realistic rotor Reynolds number of 1 x 10(6), a quasi three-dimensional translational setup was carefully generated to feature similar midspan blade loadings to the three-dimensional rotational set up of the Transonic Compressor Darmstadt. Two cases were considered, one with a laminar inflow to the rotor and one with inflow turbulence. It is found that the inflow turbulence suppresses the rotor suction side separation bubble with implications on the shock-boundary layer interaction, mainly in terms of an upstream moved shock location and changes to the shock oscillations, and the shock-related passage losses. The changes to the early development of the rotor suction side boundary layers also affects the boundary layer losses. The stator suction side boundary layer on the other hand appears insensitive to the introduction of inflow disturbances. However, a larger passage loss is found for the laminar inflow case in the stator. Additional URANS calculations of the same setup show overall good comparison with the high-fidelity results for most integral values, but lack in predictive accuracy for some details, such as shock boundary layer interaction as well as wake and passage losses.